Abstract

Sea travel mandates changes in the control of the body. The process by which we adapt bodily control to life at sea is known as getting one's sea legs. We conducted the first experimental study of bodily control as maritime novices adapted to motion of a ship at sea. We evaluated postural activity (stance width, stance angle, and the kinematics of body sway) before and during a sea voyage. In addition, we evaluated the role of the visible horizon in the control of body sway. Finally, we related data on postural activity to two subjective experiences that are associated with sea travel; seasickness, and mal de debarquement. Our results revealed rapid changes in postural activity among novices at sea. Before the beginning of the voyage, the temporal dynamics of body sway differed among participants as a function of their (subsequent) severity of seasickness. Body sway measured at sea differed among participants as a function of their (subsequent) experience of mal de debarquement. We discuss implications of these results for general theories of the perception and control of bodily orientation, for the etiology of motion sickness, and for general phenomena of perceptual-motor adaptation and learning.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1. Experiment 1: Mean stance width…

Figure 1. Experiment 1: Mean stance width (the distance between the midline of the heels)…

Figure 1. Experiment 1: Mean stance width (the distance between the midline of the heels) as a function of days.

The figure illustrates the statistically significant effect of days. The error bars represent standard error of the mean.

Figure 2. Setting and conditions for body…

Figure 2. Setting and conditions for body sway testing.

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A. Viewing of the nearby target…

Figure 2. Setting and conditions for body sway testing.

A. Viewing of the nearby target and the horizon at the dock. B. Viewing of the nearby target and the horizon at sea.

Figure 3. Experiment 2: Mean positional variability…

Figure 3. Experiment 2: Mean positional variability of the COP as a function of days.

Figure 3. Experiment 2: Mean positional variability of the COP as a function of days.

The figure illustrates the statistically significant effect of days. The error bars represent standard error of the mean.

Figure 4. Experiment 2: Mean positional variability…

Figure 4. Experiment 2: Mean positional variability of the COP during viewing of the nearby…

Figure 4. Experiment 2: Mean positional variability of the COP during viewing of the nearby target and the horizon, as a function of days.

Figure 12. Experiment 4: Mean positional variability in the AP and ML axes for participants who experienced mal de debarquement for less than 30 minutes (the Low-MD group) or more than 120 minutes (the High-MD group).

Supplementary concepts

Grant support

The study was supported by the University of Minnesota, the University of Montpellier-1, the University of Sao Paulo, and National Pingtung University of Science and Technology. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.